I'm having this issue whenever I try to install Forge 30.0.51 for Minecraft v1.15.1 client side. I'm using a Macbook Pro 2012, Version 10.12.6 (macOS Sierra)
These libraries failed to download. Try again.
org.ow2.asm:asm:7.2
org.ow2.asm:asm-commons:7.2
org.ow2.asm:asm-tree:7.2
cpw.mods:modlauncher:5.0.0-milestone.4
cpw.mods:grossjava9hacks:1.1.0
net.minecraftforge:accesstransformers:2.0.0-milestone.1-shadowed
net.minecraftforge:eventbus:2.0.0-milestone.1-service
net.minecraftforge:forgespi:2.0.0-milestone.1
net.minecraftforge:coremods:2.0.0-milestone.1
net.minecraftforge:unsafe:0.2.0
com.electronwill.night-config:core:3.6.2
com.electronwill.night-config:toml:3.6.2
org.jline:jline:3.12.1
org.apache.maven:maven-artifact:3.6.0
net.jodah:typetools:0.6.1
org.apache.logging.log4j:log4j-api:2.11.2
org.apache.logging.log4j:log4j-core:2.11.2
net.minecrell:terminalconsoleappender:1.2.0
net.sf.jopt-simple:jopt-simple:5.0.4
com.github.jponge:lzma-java:1.3
com.google.code.findbugs:jsr305:3.0.2
com.google.errorprone:error_prone_annotations:2.1.3
com.google.guava:guava:20.0
com.google.guava:guava:25.1-jre
com.google.j2objc:j2objc-annotations:1.1
com.nothome:javaxdelta:2.0.1
de.oceanlabs.mcp:mcp_config:1.15.1-20191217.105819@zip
net.md-5:SpecialSource:1.8.5
net.minecraftforge:binarypatcher:1.0.7
net.minecraftforge:installertools:1.1.4
net.minecraftforge:jarsplitter:1.1.2
net.sf.jopt-simple:jopt-simple:4.9
net.sf.jopt-simple:jopt-simple:5.0.4
net.sf.opencsv:opencsv:2.3
org.checkerframework:checker-qual:2.0.0
org.codehaus.mojo:animal-sniffer-annotations:1.14
org.ow2.asm:asm-analysis:6.1.1
org.ow2.asm:asm-commons:6.1.1
org.ow2.asm:asm-tree:6.1.1
org.ow2.asm:asm:6.1.1
trove:trove:1.0.2